Electric signaling



April 28, 1942. A. w. HORTN, JR., ErAL 2,281,441

4 ELECTRIC SIGNALING Filed Jan. a1, 1941 Pis-04mm? /MPaLsE VaLqE A TTQRNEV .,4. W Hok To/v, JR.

Patented Apr. 28, i942 UNE STATES PATENT OFFICE ELECTRIC SIGNALING Arthur W. Horton, Jr., South Orange, N. J., and Milton E. Mohr, Jamaica, N. Y., assgnors to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application January 2l, 1941, Serial No. 375,202

5 Claims.

This invention relates to signaling and particularly to the generation and transmission of electric signals and impulses.

The objects of the invention are to obtain impulses which are accurately fixed in time; to enable the phases in which the impulses occur to be varied with a high degree of accuracy; to obtain impulses that are uniform in amplitude and well dened in shape; and to realize other improvements in the generation and transmission of impulses.

These objects are attained by means of an impulse generator in which the voltage wave of a supply source is rectied and the resultant voltages applied to a resistance element, in which two discharge tubes serve respectively to limit the voltage of both alternations of the cycle to a definite value, and in which the impulses are produced by the change in voltage in the resistance element occurring during the successive intervals that the tubes are not conducting.

More specifically, an impulse generating system is provided comprising two circuit branches, each having a unilateral or rectifying element therein and a common branch including a resistance element in which the impulses are generated. When alternating current from the supply source is applied to the two circuit branches, the rectifying elements cause the current to iiow in the same direction through the resistance element for both alternations of the cycle. Two discharge tubes are also provided, one for each branch of the circuit, each tube being connected in parallel with the common resistance and the associated rectifying element. Both of these tubes ionize when the supply voltage reaches a particular value and serve to limit the voltage applied to the common resistance. As the supply voltage wave declines below the sustaining value of the tubes, when the wave approaches zero value, both tubes cease to conduct, and current ceases to flow in the common resistance element. A biasing battery is provided in the impulse generating circuit having a voltage which opposes and neutralizes the limited voltage applied to the common resistance while the tubes are conducting. During the brief period, however, that the tubes are non-conducting, as the voltage wave is passing through zero, the voltage in the common resistance element, which hasl been in opposition to the biasing battery voltage, decreases and rises again. During this interval the voltage of the biasing battery predominates to produce the desired impulse.

A feature of the invention, therefore, is a the source I.

generator in which an impulse occurs each time the supply wave passes through the Zero value and in which the peak of each impulse produced occurs exactly at the point of time when the supply Wave crosses the axis from one alternation to the next. With such a generator it is possible to fix the position of the impulse in time by controlling the frequency and phase of the supply source. By providing a plurality of these generators and supplying them with alternating current of desired phases impulses of corresponding phases are produced and may be used for signaling purposes.

. These and other features of the inventionl will be discussed more fully in the following detailed specication.

t. In the drawing accompanying the specificaion:

Fig. 1 discloses an impulse generating system incorporating the features of this invention;

Fig. 2 is a graph depicting the formation and position of the impulses; and

Fig. 3 is a diagram of a signaling system incorporating the impulse generator.

Referring first to Fig. l, the generating system shown therein comprises a supply source of alternating current I having any desired voltage and frequency. The supply source I is connected to the primary winding of a transformer, and the secondary windings 3 and 4 of the trans'- former are included respectively in two rectifying circuits 5 and 6. The -rectifying circuit 5 also includes a resistance element l, a rectifier 8, resistance element 9 and conductor II). The rectifying circuit 6 includes, in addition to the secondary winding Il, the resistance element II, the rectier I2, the common resistance element' 9 and the common conductor IB, which is connected to battery I6. One output terminal I3 of the impulse generator is connected to the resistance element 9. The other output terminal I5 1s connected to ground. The terminals I3 and I5 may be connected to any desired impulse circuit, such as the circuit I'I.

A space discharge tube I8, preferably of the gas-filled type, is connected across the' rectifying circuit 5 for the purpose of limiting the current flowing through the resistance element 9 durmg half of each cycle of the voltage wave of Similarly a discharge tube I9 is lconnected across the rectifying circuit 6 for the purpose of limiting the current flowing in the resistance element 9 during the alternate halfy of each cycle of the source I.

kInk consideringv the operation of this impulse system it may be assumed that the curve 20 in Fig. 2 represents the voltage wave applied to the rectifying circuits 5 and 6 by the secondary windings 3 and 4 of the transformer, that the curve 50 represents the rectied voltage across resistor 9 as a result .of voltage wave 29, that curve 5I represents the voltage of biasing battery I6, and that curve 22 represents the impulse Voltage across resistor 9 which is the resultant of voltages 50 and 5I. Also it may be assumed that as this wave passes through the zero value and commences to rise in the positive direction the upper terminal of winding 3 becomes positive and the lower terminal of winding 4 becomes negative in polarity. This initial voltage appearing across the winding 3 is not suicient to discharge the tube I8 and is of the wrong polarity to cause current to iiow through the rectiiier 8 and resistance 9. The Voltage across the other Winding 4 is also insufficient in the beginning to discharge the tube I9, but the polarity 'of this Voltage is 'such that current ows from the upper terminal of 'winding 4 over conductor I0 through resist- 'ance 9, rectier I2 in the conducting direction,

resistance II to the lower terminal of winding 4.

As the voltage rises, the current in resistance 9 'continues to increase, and the voltage across the tubes IB and I9 rises. The Value of resistance 9 is chosen sufficiently high to cause the Voltage across the t'ube I9 to rise to the ionizing value 'at the desired point in the cycle of the applied voltage wave 29. When, therefore, the voltage wave 29 reaches the desired instantaneous value, represented by the ordinate 2| in Fig. 2, the tube I9 discharges. Also at this time the voltage across tube I8 will have reached the ionizing value, and hence this tube discharges. Tube I8 does not aiiect the current in resistance 9, vhowever, since rectier 8 does not permit Icurrent to iiow 'during this half cycle. But, the tube I9, having discharged, maintains the voltage across its electrodes constant 'at the value 2'I notwithstanding the continued increase -in the applied voltage. Therefore, the Voltage across the resista'nce element 9, andv likewise the current iowing therein, remainv at 'constant values.

The current in resistance element 9 Yflows in the direction indicated by the arrow, and the polarity of the resulting voltage is such that the output terminal I3 is made negative with respect to the positive pole of lthe `biasing 'battery IS by the amount of the Voltage appearing `across the r-esistance 9. The terminal I5 is 4connected to ground, and the conductor I Il is connected to the 'positive pole of biasing battery Iii. The voltage of 'this battery may be chosen at a value substantially 'equal to the Voltage generated in resistance 9 when either tube is conducting. Hence no 'voltage difference appears across the termi- 'nais I3 and I5, and no impulse is present in the impulse circuit I1.

This condition prevails while the voltage wave '20 is rising to its maximum value and '-until it again declines to the value represented by the Iordinate 2 I. When the wave reaches the ordinata value `2I, that is, as it approaches the zero value, the tube `I9 'quenches so that thecurrent flowing in the resistance element 9 now becomes a function of the applied voltage wave. Also the tube 'I8 vquenohes as the voltage wave approaches the A'ordinate value 2-I. -As the Voltage wave `2|) continues to decline toward the zero ordinate, the `current in resistance element 9 -declines 4correspondingly, and the voltage difierenceacr'o'ss the output terminals I3 and I5, due to :battery I6,

rises in value directly in proportion to the decline of the voltage across the resistance element 9. An impulse, therefore, appears in the circuit I'I, which increases to its maximum value at the instant the applied voltage wave 2 reaches zero. As the applied voltage wave passes through the zero point and rises in the opposite direction current again flows through the element '9, in the direction indicated by the arrow, through the rectier 8 and resistance element 1 to the upper terminal of the transformer winding 3. Similarly when the applied voltage wave reaches the ordinate value 2l, tubes I8 and I9 discharge, and the tube I8 serves to limit and iix the voltage across the resistance element 9 until the applied wave again declines to the ordinate value 2l. While the tube I8 is conducting the voltage across the resistance element 9 is limited to the Vsame value as before mentioned, and no potential difference appears across the terminals I3 and I5. When the applied voltage wave 20 reaches the value 2l in the 4nagative halfof its cycle, the tubes I8-and I9 quench, and the voltage across the resistance 9 declines to cause the appearance of another impulse in the circuit I1.

Thus for each cycle of the applied wave two impulses of positive polarity are produced', and these impulses are accurately iixed at the point in time when 'the vapplied wavepasses through the Zero values. These impulses are illustrated by the curve 22 in Fig. 2 which shows `the .neutralizing effect of the biasing battery I6 during the major part of each alternation.

Obviously, the magnitude of the impulse may be controlled by varying the sustaining voltage-of the discharge tubes I8 and I9.

If it is desired to have the .generator produce negative impulses it is only necessary to reverse the polarity of biasing battery and to reverse the direction of -re'ctiers 8 and l2.

Fig. 3 illustrates one 'of the many useful applications of the impulse generating system shown in Fig. A1. Assume for example that fit lis *desired to transmit -a plurality of different signais over the single transmitting vconductor 23. At the transmitting 'end 'of the line a source of alternating current 24 is provided. Also there is provided a suitable phase generator 25 whereby aplurality of different .phases are derived ifrom the original source 24. These phases, fof which therein-ay be ten for example, appear on the respective phase `supply circuits 26, 21., 28, .29, 30,., 3-I, 32. vvoltages of any desired phases to represent the required signal are applied to the transmittin-g conductor 23 -by 'anysuitable.'selectivemeans, "Such as the dswitches 33,134, 35., etc,

At the receiving fend fof the lsystem an impulse genera-tor 35 is provided, like the Vgenerator dis;- closed in detail in Fig. 1. The generator @Evre- `spends to the incoming wave .of any particular phase and produces im-pulses inv 'the output :circuit 31, and these impulses areapplied tothe .electrodes of a plurality of register tubes 38, 39, 40, 4I etc. At the saine time impulses'of leach of .the ten Idile'rent phases fare being applied to the other electrodes of fthe respective register tubes.

'These impulses are produced by Va mechanism Fig. 1, except that they are of the opposite polarity. For example, the generator 44 produces negative impulses of phase No. 1 and applies these impulses to the electrode of tube 38, generator 45 produces negative impulses of phase No. 2 and applies them to the electrode of tube 39, and so on for the remaining generators 46, 41, etc. The generator 36 however produces impulses of positive polarity and applies them over the common conductor 31 to all of the register tubes. Hence, when current of phase No. 1 is transmitted over the signal conductor 23 the positive impulses of this phase match with those applied to tube 38 and not with those applied to any of the remaining tubes. Consequently tube 38 is selectively operated to the exclusion 'of the other tubes to register the transmitted signal.

Register tubes suitable for use in a system of this kind are disclosed in the copending application of W. H. T. Holden, Serial No. 361,537, led October 17, 1940. 'Ihe Holden application also discloses impulse generators for generating impulses of opposite polarities.

What is claimed is:

1. The combination in an impulse system of an impulse conductor, an impedance element in circuit with said impulse conductor, two rectifying circuits including said impedance element in common, a source for producing an alternating voltage wave, means for applying said wave to said rectifying circuits, rectiers in said circuits for causing current to iiow in the same direction in said impedance element during both alternations of the cycle of said wave, discharge devices in both of said rectifying circuits which conduct and cease to conduct in response to the rise and fall of said wave, said devices when conducting serving to limit the current flowing in said impedance element, and means effective during the interval that said discharge devices are not conducting for producing an impulse in said impulse conductor.

2. The combination in an impulse system of an impulse conductor, a resistance element in circuit with said conductor, two rectifying circuits including said resistance element in common, a source for producing an alternating voltage wave, means for applying said wave to said rectifying circuits, rectiers in said circuits for maintaining the same polarity for the voltages applied across said resistance element throughout the cycle of said voltage wave, discharge tubes in said rectifying circuits which conduct when said voltage wave rises to a denite value and cease to conduct when said wave falls to a deiinite value, said discharge tubes serving to limit to a denite value the voltage applied across said resistance element, and means eiective during each interval that said discharge tubes are not conducting for producing an impulse in said impulse conductor.

3. The combination in an impulse system of an impulse conductor, a resistance element in circuit with said conductor, a source for producing an alternating voltage wave, two wave receiving circuits including said resistance element in common, means for applying said wave to said receiving circuits, rectiers in said circuits for maintaining the same polarity for the voltages produced across said resistance element in response to said voltage wave, a separate discharge tube for each of said receiving circuits, said tubes serving to limit to a predetermined value the voltage across said resistance element, and a second source of voltage for neutralizing the Voltage across said resistance element while said tubes are conducting and for producing an impulse in said impulse conductor in response to the voltage change across said resistance element during the period said discharge tubes are not conducting.

4. The combination in an impulse system of an impulse circuit, a resistance element in said impulse circuit, a source for producing an alternating voltage wave, two wave receiving circuits including said resistance element in common, means for applying said voltage wave to said receiving circuits, rectifiers in said receiving circuits for maintaining the same polarity for the voltages produced across said resistance element in response to said applied wave, a separate discharge tube connected to each of said receiving circuits, both of said tubes becoming conducting when said voltage wave reaches a predetermined value in either direction, said tubes serving when conducting to limit to a definite value the voltage across said resistance element, and a second source of voltage connected to said impulse circuit to oppose and neutralize the voltage across said resistance element while said tubes are conducting, said second source of voltage serving to produce an impulse in said impulse circuit in response to the change in voltage across said resistance elementl during the interval said tubes are not conducting.

5. The combination in an impulse system of an impulse conductor, an impedance element in circuit with said conductor, two rectifying circuits including said impedance element in common, a source for producing an alternating voltage wave, means for applying said wave to said rectifying circuits, rectiers in said circuits for causing current to flow in the same direction inf said impedance element during both alternations of the cycle of said wave, discharge devices in both of said rectifying circuits which conduct and cease to conduct in response to the rise and fall of said wave, said devices when conducting serving to limit the current iiowing in said impedance element, and means effective during the interval said discharge devices are not conducting for producing in said impulse conductor an impulse having a maximum amplitude which occurs coincident with the passing of said alternating voltage wave through its zero value.

ARTHUR W. HORTON, JR. MILTON E. MOHR. 

